This invention relates to a combustion apparatus and method which is particularly effective at combusting ammonia in ammonia containing streams which are produced by certain oil refinery processes.
It is typical in a refinery to utilize a desulfurization unit to hydrotreat an oil stream to remove sulfur therefrom. Hydrogen reacts with sulfur in the oil stream to produce hydrogen sulfide (H.sub.2 S) and also reacts with nitrogen in the oil stream to produce ammonia (NH.sub.3). Therefore, the product gas stream produced by the desulfurization unit includes hydrogen sulfide as well as ammonia. Removal of a substantial amount of the hydrogen sulfide and ammonia is required by stringent pollution laws. It is also economically desirable to remove the hydrogen sulfide in order to recover sulfur therefrom.
In order to remove such hydrogen sulfide and ammonia from the product gas stream as produced by the desulfurization unit, the product gas stream is first water washed to absorb some of the hydrogen sulfide and most of the ammonia. The resulting "sour" water is passed through a water stripper to thereby produce a sour gas containing ammonia, hydrogen sulfide and water vapor. After water washing of the product gas stream, the product gas stream is then treated with amine to absorb the remainder of the hydrogen sulfide. An amine stripper is utilized to strip the amine to leave an "acid" gas containing primarily hydrogen sulfide.
It is well known to recover sulfur from hydrogen sulfide containing gases such as acid gas and sour gas. The most typical process employed is called the "Claus" reaction wherein only a portion of the hydrogen sulfide is burned to yield a mixture of sulfur dioxide, water vapor and the remaining unburned hydrogen sulfide. This mixture is then cooled to cause the reaction of the remaining hydrogen sulfide and SO.sub.2 and consequent formation of sulfur. Any unreacted hydrogen sulfide and sulfur dioxide is passed over a bauxite catalyst to complete the sulfur recovery process.
Although prior processes have been effective at decomposing hydrogen sulfide and recovering sulfur, efforts at decomposing the ammonia from sour gas in the combustion step of such processes have not been particularly effective. A substantial amount of ammonia, as noted previously, must be removed to meet pollution standards. In addition, any remaining ammonia in the output stream of the combustion furnace, even if meeting pollution standards, can be corrosive to equipment used downstream in the sulfur recovery process. Therefore, it is particularly desirable to maximize the removal of ammonia from sour gas streams.